EPA 910/9-40*072







United States
Environmental Protection
Agency
Region 10
1200 Sixth Avenue
Seattle. WA 98101

Surveillance & Analysis
August 1980
	
	
	
Water Quality Studies Of the
Spokane River between
Coeur D'Alene, Idaho and
Post Falls, Idaho
1978 - 1979

- *": '*
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! . .

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EPA 910/9-80-072
July 1980
WATER QUALITY STUDIES
OF THE
SPOKANE RIVER
BETWEEN
COEUR D'ALENE, IDAHO
AND
POST FALLS, IDAHO
1978 - 1979
Prepared by
John R. Yearsley
EPARegion 10
1200 Sixth Avenue
Seattle, Washington 98101

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THIS DOCUMENT" IS AVAILA8LE IN LIMITED QUANTITIES
THROUGH THE U.S. ENVIRONMENTAL PROTECTION AGENCY,
SURVEILLANCE AND ANALYSIS DIVISION, 1200 SIXTH
AVENUE, SEATTLE, WASHINGTON 98101

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TABLE OF CONTENTS
CHAPTER	PAGE
INTRODUCTION	 1
FIELD STUDIES	 5
RESULTS			 7
CONCLUSIONS	 51
BIBLIOGRAPHY	 53

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LIST OF FIGURES
FIGURE	PAGE
1.	Map of the Spokane River between Coeur d'Alene and
Post Falls, Idaho	 2
2.	Sample station locations in the Spokane River water
quality studies	 3
3.	River cross-sections at various locations in the Spokane
River between Coeur d'Alene and Post Falls	 8
4.	Longitudinal profile along the approximate centerline of
the Spokane River between Coeur d'Alene and Post Falls	 9
5.	Average, maximum and minimum water temperatures in the
Spokane River during Survey 1	 12
6.	Average, maximum and minimum water temperatures in the
Spokane River during Survey II	 13
7.	Average, maximum and minimum water temperatures in the
Spokane River during Survey III.....	 Id
8.	Average, maximum and minimum water temperatures in the
Spokane River during Survey IV	 15
9.	Average vertical temperature profile at Ford Rock during
Surveys I, II, III and IV			 17
10.	Average, maximum and minimum dissolved oxygen
concentrations in the Spokane River during Survey 1	 21
11.	Average, maximum and minimum dissolved oxygen
concentrations in the Spokane River during Survey II	 22
12.	Average, maximum and minimum dissolved oxygen
concentrations in the Spokane River during Survey III	 23
13.	Average, maximum and minimum dissolved oxygen
concentrations in the Spokane River during Survey IV	 24
14.	Average, maximum and minimum dissolved oxygen saturation
levels in the Spokane River during Survey 1	 2?
15.	Average, maximum and minimum dissolved oxygen saturation
levels in the Spokane River during Survey II	 26

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PAGE
27
28
29
30
33
34
35
36
37
38
40
41
46
48
Average, maximum and minimum dissolved oxygen saturation
levels in the Spokane River during Survey III	
Average, maximum and minimum dissolved oxygen saturation
levels in the Spokane River during Survey IV	
Average vertical dissolved oxygen concentration profile
at Ford Rock during Surveys I, II, III and IV	
Average vertical dissolved oxygen saturation level
profile at Ford Rock during Surveys I, II, III, and IV..
Average, maximum and minimum total phosphorus
concentrations in the Spokane River during Survey II....
Average, maximum and minimum total phosphorus
concentrations 1n the Spokane River during Survey IV....
Average, maximum and minimum total nitrogen
concentrations in the Spokane River during Survey II....
Average, maximum and minimum total nitrogen
concentrations in the Spokane River during Survey IV....
Average, maximum and minimum total organic carbon
concentrations in the Spokane River during Survey II....
Average, maximum and minimum total organic carbon
concentrations in the Spokane River during Survey IV....
Average, maximum and minimum ultimate BOO in the
Spokane River during Survey II	
Average, maximum and minimum ultimate 800 in the
Spokane River during Survey IV	
Water clarity in the Spokane River during Surveys I, II,
III and IV as measured by Secchi disk depths...	
Qualitative assessment of Equisetum in the
Spokane River during Survey IV.			

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LIST OF TABLES
TABLE	PAGE
1.	Dates of field studies on the Spokane River
between Coeur d'Alene and Post Falls	 5
2.	Methods used to obtain measurements in the field
during Surveys I - IV on the Spokane River	 6
3.	Methods used for samples shipped to EPA Region 10
Laboratory during Surveys II and IV on the Spokane River... 6
4.	Provisional values of daily discharge in the Spokane
River, daily diversions to the Rathdrum Prairie Project
and daily elevations of Lake Coeur d'Alene during
Surveys I - IV	 11
5.	Ultimate 800 and deoxygenation rates in the Spokane
River estimated from samples collected during Survey II.... 39
6.	Ultimate BOD and deoxygenation rates in the Spokane
River estimated from samples collected during Survey IV.... 39
7.	Estimated loading rates of total organic carbon, total
phosphorus, total nitrogen and ultimate BOO to the
Spokane River from Lake Coeur d'Alene during
Surveys II and IV	 42
8.	Concentrations and estimated loadings of total organic
carbon, total Kjeldahl nitrogen, ammonia nitrogen,
nitrite-plus-nitrate-nitrogen, dissolved orthophosphate
and total phosphorus to the Spokane River from the
Coeur d'Alene sewage treatment plant during
Surveys II and IV	 43
9.	5-day BOO as a function of dilution for samples
collected from the City of Coeur d'Alene sewage treatment
plant on 7/31/79 and 8/1/79	 44
10. 5-, 10-, 15-, and 20-day BOD measurements of samples
collected from the City of Coeur d'Alene sewage treatment
plant on 7/31/79 and 8/1/79	 45

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INTRODUCTION
The Spokane River between the outlet of Lake Coeur d'Alene and Post Falls
Dam 1n Idaho (Figure 1) 1s a multi-purpose reservoir providing
recreation, irrigation, navigation and hydroelectric power generation
benefits. Studies by the U.S. Geological Survey (USGS) (Drost and
Seitz(1978)) suggest that this segment of the Spokane River contributes
an average of 150 c.f.s. to the Rathdrum Prairie Aquifer, an important
source of water supply for the Spokane Valley. The river segment also
serves as the receiving water of the effluent from the City of
Coeur d'Alene's sewage treatment plant.
Due to population growth, both Post Falls and Coeur d'Alene are
increasing the sizes of their waste treatment facilities. In order to
design these facilities so that the water quality of the Spokane River is
maintained, it is necessary to estimate the maximum level of waste
discharge consistent with this goal. A proper estimate of this level
requires substantial study of the river system. This report describes a
program of study conducted by Environmental Protection Agency, Region 10,
designed to collect data necessary to estimate the impact of waste
discharge upon dissolved oxygen under summer low-flow conditions. Field
measurements of certain nutrient levels in the treatment plant and the
receiving water, algal assays and a reconnaissance survey of aquatic
plants were adjunct observations which may prove helpful in determining
the effect future discharges will have on the trophic status of the river
segment.
-1-

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Map of the Spokane River between Coeur D'Alene and Post Falls,
Idaho
Post Fulls
Fiyuie 1

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008
Sample Station Locations in
the Spokane River Water
Quality Studies of December
5-6, 1978, July 31 - August 2,
1979, August 16-17, 1979 and
September 18-20, 1979
i
CO
i
(2) River Cross sections.
Temperature, Dissolved
Oxygen, Water Clarity
River Cross sections.
Temperature, Dissolved
^ Oxygen, pH, Conductivi
ty. Water Clarity
River Cross-sections,
Temperature, Dissolved
Oxygen, pH, Conductivi-
ty, Algal Assay, Water
Clarity
Coaur D'Alene
Figure 2

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FIELD STUDIES
The field study program included four surveys of this segment of the
Spokane River. Table 1 shows the survey dates and the type of
information collected during each survey.
Table 1 Dates of field studies on the Spokane River between Coeur
d'Alene and Post Falls, and type of information collected
Survey	Date
I	December 5-6, 1978
II	July 31-August 2, 1979
III	August 16-17, 1979
Type of Information
River cross-sections, temperature,
dissolved oxygen, water clarity
Temperature, dissolved oxygen, pH,
conductivity, BOD, phosphorus,
nitrogen, water clarity
Temperature, dissolved oxygen, pH,
conductivity, water clarity
IV September 18-20, 1979 Temperature, dissolved oxygen, pH,
conductivity, BOD, phosphorus,
nitrogen, algal assay, aquatic plant
survey, water clarity
Methods
The sampling program included observations which we made in the field, as
well as measurements made from samples shipped to the EPA Regional
Laboratory at Manchester, Washington. Table 2 shows the measurements we
made in the field and the type of instruments used.
-5-

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Table 2 Methods used to obtain measurements in the field during Surveys
I-IV on the Spokane River between Coeur d'Alene and Post Falls
Measurement
Method
Temperature
Dissolved oxygen
pH
Conductivity
Water clarity
River cross-sections
Thermistor*, mercury thermometer
Polarographic electrode*, Winkler
(azide modification)
Electrode*
Electrode*
Secchi disk
Recording fathometer
* Module of Hydrolab Surveyor Model 6D
Those samples for which measurements were made at the laboratory, were
stored in polyethylene containers, packed in ice and shipped via air
freight. For those measurements made in the laboratory, the method is
shown in Table 3 and described by EPA's (1979) Methods for Chemical
Analysis. Location of sampling stations and type of measurement at each
station are shown in Figure 2.
Table 3 Methods (EPA (1979)) used for those samples shipped to the EPA
Region 10 Laboratory during Surveys II and IV on the Spokane
River between Coeur d'Alene and Post Falls
Parameter
5-day BOD
10-day BOD
15-day BOD
20-day BOD
Arnnoni a-ni trogen
N i tr i te+n i trate-n i trogen
Total Kjeldahl nitrogen
Total phosphorus
Dissolved orthophosphate
Total organic carbon
Method
5-day -20C incubation
10-day -20C incubation
15-day -20C incubation
20-day -20C incubation
Auto Analyzer II
Auto Analyzer II
Block digestion + Auto Analyzer II
81ock digestion + Auto Analyzer II
Auto Analyzer II
Combustion or oxidation
-6-

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RESULTS
Receiving Waters
Cross-Sectional Character!sties
Transverse profiles of the Spokane River bottom, taken during Survey I at
several locations between Coeur d'Alene and Post Falls, are shown in
Figure 3. Longitudinal profiles of the bottom, along the approximate
centerline of the river are shown in Figure 4. According to the USGS,
the average elevation of the water surface of the Spokane River, on the
day'the profiles were made, was 2123.6 feet above mean sea level.
Important features, which may have an impact upon water quality, include:
1.	The broad sill between Green's Ferry and Ford Rock.
2.	The deep "holes" on either side of Ford Rock.
3.	The river bottom behind Post Falls Dam is approximately 2092
feet above mean sea level. Water is withdrawn from the river
through a penstock with an inlet diameter of 11'3" and
centerline at 2108.1 feet above mean sea level.
River Flow
We made no measurements of river flow during our four surveys. Instead
we have relied upon the flow records maintained by the USGS. Provisional
-7-

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Outlet
Gibbs
Atlas
Huetter

001

111.0
V
. . - J
003
108.6
\_	J
Harbor Island
Black Bay
On Vertical Scale (Feet)
10
21
301
401
50"
Bridge @
Post Falls
Horizontal Scale (Feet)
' ' ' 1000
River Cross-sections at Various Locations in the Spokane River
between Coeur D'Alene and Post Falls (Pool Elevation = 2123.6
Feet above Mean Sea Level)
Figure 3

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003
002
001
004
003A
003
=r
0
05
O
o
I
I
4A
0(
)4

	


008 0
O
i
Sj
36 1



^
i50
Approximate Horizontal Scale (Miles)
1 0
0 5
Vertical Scale (Feet)

Longitudinal Profile along the Approximate Centerline of the Spokane River between
Coeur D'Alene and Post Falls (Pool Elevation = 2123.6 Feet above Mean Sea Level)

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values of the Spokane River discharge at Post Falls, diversions to the
Rathdrum Prairie Project and elevation of Lake Coeur d'Alene during the
four surveys are shown in Table 4.
Temperatures
Vertical profiles of temperature were made at several locations (Figure
2) in the Spokane River during each of the four surveys. Average,
maximum and minimum temperatures, as measured during these surveys, are
shown in Figures 5 through 8. Averages were computed as simple
arithmetic average of all values measured at a station during a
particular survey. This kind of average will result in a biased estimate
of the mean if the vertical sampling interval is not uniform. The
vertical sampling interval was not uniform during Surveys II, III, and
IV. A comparison of simple averages and depth-weighted averages, at
three locations where bias might be expected, showed a maximum difference
of 0.2C. Under these circumstances, we felt that the simple average
would be adequate. The reported maxima and minima are the highest and
lowest temperature, respectively, measured at each sample location during
the particular survey. It should be kept in mind that these maxima and
minima were obtained over a period of as much as three days.
Furthermore, the accuracy with which we could locate a particular station
was dependent upon wind speed and river current. In those parts of the
river, such as at Ford Rock, where the depth changed rapidly we were not
always able to obtain data from the same depths. There has been no
attempt to account for these difficulties in computing either the mean or
extreme values.
-10-

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Table 4 Provisional values of dally discharge in the Spokane river, daily diversions to the
Rathdrum Prairie Project and daily elevations of Lake Coeur d'Alene durinq EPA
Region 10's Surveys I - IV.
Daily Average Discharge Dally Average Diversion
of the Spokane River	to the Rathdrum	Daily Average Elevation

@ Post Falls
Prairie Project
of Lake Coeur d'Alene
Date
(cfs)
(cfs)
'ft above MSLl
12/5/78
1530
0
2123.^9
12/6/78
1540
0
2123.5?
7/31/79
628
46
2127.90
8/1/79
618
46
2127.88
8/2/79
636
45
2127.87
8/16/79
700
32
2127.78
8/17/79
694
32
2127.80
9/18/79
1350
0
2126.59
9/19/79
1350
0
2126.55
9/20/79
1350
0
2126.53

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Figure 5. Average, maximum and minimum v/ater temperatures in the Spokane
River during Survey I (December 5-6, 1978).
1	1	1	II	I	I	1	T
" I * * * * * *
J	1	I	I	I	I			I	I	L
103 104 105 106 10? 108 109 110 111 112
SPOKANE RIUER HILE

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Figure 6. Average, maximum and minimum water temperatures 1n the Spokane
River during Survey II (July 31 - August 2, 1979).
i	1	1 i i i	1	1	r
li
i
I I
i
I f
J	I	I	I	I	I	I	I	L
103 104 105 106 107 108 109 110 111 112
SPOKANE RIUER MILE

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Figure 7. Average, maximum and minimum water temperatures in the Spokane
River during Survey III (August 16-17, 1979).
I
T
E
II
P
E
R
A
T
U
R
E
D
E
G
112
SPOKANE RIUER NILE

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Figure 8. Average, maximum and minimum water temperatures 1n the Spokane
River during Survey IV (September 18-20, 1979)
30
<_n
I
T
E
(1
P
E
R
A
T
U
R
E
D
E
G
25
20
15
10
"1*1 i I I
J I
J	i	I	I	I	I	i	I	I
103 104 105 106 10? 108 109 110 111 112
SPOKANE RIVER P1ILE

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During Survey I (Oecember 5-6, 1978), the average water temperature
varied from 4.0C to 5.1C. The highest average temperature of
5.1C was measured near the outlet of Lake Coeur d'Alene (River Mile
110.0). The average temperature decreased downstream to a minimum of
o
4.2 C at Green's Ferry (River Mile *03.T), then increased slightly to
4.6C at Post Falls (River Mile 102.5). The maximum vertical
variations (difference between maximum and minimum temperature at each
sample station) in temperature at any of the sampling locations was
0.9C at Post Falls.
During Surveys II (July 31-August 2, 1979) and III (August 16-17, 1979)
water temperatures varied from 18.5C to 24.5C. The longitudinal
variation of average temperature was less than 0.8C during both
surveys. There was a substantial vertical variation in temperature,
however, particularly at those locations such as Ford Rock (R.M. 103.$)
and Post Falls Dam (R.M. 102.2) where water depths equalled or exceeded
10 meters. Ouring Surveys II and III vertical variations at Ford Rock
were 5.1C and 5.0C, respectively, and at Post Falls Dam were
4.2C and 3,3C, respectively. At the shallower, upstream stations
\l.O	0
(R.M. HO>3 to R.M. 106-f4) the vertical variation was between 0.7 C and
1.8C during Survey II and between 1.0C and 1.9C during Survey
III. Surface temperatures, during both surveys increased downstream.
The difference in vertical variation between the shallower, upstream
stations and the deeper, downstream stations was due to the colder water
found at depths of 10 meters and below. At Ford Rock, for example, the
temperature at 10 meters and below was between 19.0C and 20.7C
-16-

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I
Figure 9. Average vertical temperature profile at Ford Rock (Spokane
River Mile 103.3) Surveys I, II, III and IV.
]*'
I
/' /
I
i
< i
/
/
sukucv i
SURUCV II
SURVEV III
SURUEV IU
5	10	15	20	25	36
TEMPERATURE - DEQ. C.

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during Survey II (Figure 9). Water temperatures (USGS provisional data)
in the Spokane River below Post Falls (Spokane River Mile 100.7) on June
25, 1979 and July 23, 1979, were 18.0C. and 24.0C., respectively.
If one assumes that the temperature increased linearly from June 25, 1979
to July 23, 1979, then the temperature 1n the Spokane River would have
been 19.0C. on approximately July 1, 1979. Given these assumptions,
one could then estimate the approximate "age" of the 19.0C. water at
Ford Rock on July 31, 1979, to be a little more than four weeks. By the
middle of August, when Survey III was conducted, the warmer, surface
water had mixed to 10 meters raising the temperature to between 21.3
and 22.0C. Temperatures at, and below, 15 meters during Survey III
were comparable to those measured during Survey II. At the time of
Survey III, then, the "age" of the water at Ford Rock, for depths equal
to, and greater than, 15 meters, was on the order of six weeks. This
characterization of the thermal structure at Ford Rock does not take into
account the effect of the drop in air temperature and the substantial
precipitation which occurred August 14 and 15, 1980; the effect is
reflected by the drop in average temperature between Surveys II and III.
The point to be made, however, is that the depth of the thermocline at
Ford Rock increased from Survey II and III, and that water below the
thermocline remained at essentially a constant temperature during this
period.
Increased river flow and cooler weather resulted in nearly uniform, but
lower average temperature in Survey IV (September 18-20, 1979), compared
to Surveys II and III. Vertical variations in temperature were equal to,
-18-

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or less than, 2.0C at all sample locations. Minimum water
temperatures at the bottom were similar at all sample stations,
regardless of depth.
Dissolved Oxygen
Average, maximum and minimum dissolved concentration and saturation
levels measured during the four surveys are shown in Figures 10 through
13 and 14 through 17. Figures 18 and 19 show vertical profiles of
concentration and saturation, -respectively, at Ford Rock.
Dissolved oxygen concentrations and saturation levels were nearly
uniform, both longitudinally and vertically, during Survey I (December
5-6, 1978). Concentrations ranged from 9.8 mg/1 to 10.7 mg/1 and
saturation levels from 80.8% to 89.6%.
The response of dissolved oxygen to elevated water temperatures and
reduced stream flow was reflected in the observations of Surveys II (July
31-August 2, 1979) and III (August 16-17, 1979). During Survey II,
dissolved oxygen saturation levels generally exceeded saturation at the
surface of the water, but were always less than saturation at the
bottom. At the shallower stations (R.M. 111.0 to 105.5) the saturation
levels at the bottom were equal to, or greater than, 84.8%. However, at
the deeper, downstream stations, saturation levels as low as 33.0% were
measured.
-19-

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Despite the fact that water temperatures had dropped, the dissolved
oxygen conditions were worse during Survey III (August 16-17, 1979) than
during Survey II. Surface values of dissolved oxygen at the two upstream
stations (R.M. 111.0 and 110.4) were above saturation levels. Stations
downstream from there had levels ranging from 86.8% to 95.6%. Saturation
levels at the bottom were less than 85.6% at all stations, with minimum
levels of 2.3% to 10.6% found at the bottom for the three downstream
stations (R.M. 103.3, 102.5 and 102.2).
The overall reduction in dissolved oxygen during Surveys II and III are
related to the summer low-flow conditions of long residence time and high
water temperature. The particularly severe problems at the deep,
downstream stations are a result of topographical influences (Figure 4)
acting in concert with the development of thermal stratification. The
water at depth in these places is prevented from mixing with the main
river by the density gradient which suppresses vertical movement, and by
the bottom topography or turbine invert depth which suppresses downstream
movement. As a result, the water in these places has little opportunity
reaeration and substantial opportunity for deoxygenation. Minimum
concentrations at Ford Rock and Post Falls were 2.9 mg/1 and 2.8 mg/1,
respectively, during Survey II, and 0.5 mg/1 and 0.9 mg/1, respectively,
during Survey III.
By the time of Survey IV (September 18-20, 1979), with river flows rising
and water temperature dropping, dissolved oxygen conditions improved
substantially. Saturation levels varied between 86.0% and 100.7%, while
concentrations varied from 7.5 mg/1 to 8.7 mg/1.
-20-

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Figure 10. Average, maximum and minimum dissolved oxygen concentrations
in the Spokane River durina Survey I (December 5-6, 1978).
15
I
ro
D
I
S
S
0
t
V
E
D
0
X
Y
G
E
N
II
G
/
L
ie
i
if
I
X
i
J	I	I	I	I	I	I	I	L
103 164 105 106 10? 108 109 110 111 112
SPOKANE RIUER HUE

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Figure 11. Average, maximum and minimis dissolved oxygen concentrations In
the Spokane River during ;Survey II (July Jl-August 2, 1979)
15
i
no
ro
i
D
I
S
S
0
L
V
E
D
0
X
Y
G
E
N
n
G
/
L
10
i I
i
i
j	1	1	i	i	i	i	i	i
103 104 105 106 10? 108 109 110 111 112
SPOKANE RIUER MILE

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I
Figure 12. Average, maximum and minimum dissolved oxygen concentrations
in the Spokane River during Survey III (August 16-17, 1979).
112
SPOKANE RIVER MILE

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Figure 13. Average, maximum and minimum dissolved oxyaen concentrations in
the Spokane River during Survey IV (September 18-20, 1979).
15
I
ro
-P
i
D
I
S
S
0
L
U
E
D
0
X
Y
G
E
N
n
G
/
L
10
5 -
103 104 105 106 107 108 109 110 111 112
SPOKANE RIUER MILE

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Figure-14. Average, maximum and mint'num dissolved o*ygen saturation levels
in the Spokane River during Survey I (December 5-6, 1978).
ro
en
I
D
I
S
S
0
L
U
E
D
0
X
Y
G
E
N
S
A
120
100
80
60
40
20
i i
i
i
i
j	i	i	i	i	i	i
103 104 105 106 107 108 109 110 111 112
SPOKANE RIVER MILE

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Figure 15. Average, maximum and minimum uibbuiveu oxygen saturation levels
in the Spokane River during Survey II (July 31 - August 2, 1979).
120
I
ro
I
D
I
S
S
0
L
U
E
D
0
X
Y
G
E
N
S
A
T
iee
80
60 -
40 -
20 -
103 104 105 106 107 108 109 110 111
112
SPOKANE RIUER I1IIE

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Figure 16. Average, maximum and minl'num dissolved oxygen saturation
levels in the Spokane River during Survey III
120
i
i
D
I
S
S
0
L
U
E
D
0
X
Y
G
E
N
S
A
T
100 -
80
0
40
20
112

SPOKANE RIUER MILE

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, I
Figure 17. Average, maximum and minimum dissolved oxygen saturation levels
in the Spokane River during Survey IV (September 18-20, 1979).
I
ro
00
l
D
I
S
S
0
L
U
E
D
0
X
Y
G
E
N
S
A
T
120
100
80
60
<40
20
:: X
1 i i
I
i i
J	I	I	1	I	I	I	I	L
103 104 105 106 107 108 109 110 111 118
SPOKANE RIUER MILE

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Figure 18. Average vertical dissolved oxygen concentration profile at
Ford Rock (Spokane RiveriMile 103.3) during Surveys I, II, III,
and IV.
		SURVEY I
		SURVEY II
		SURVEY III
		SURVEY IV
/

s
/
f:
:l
 I
J

_L
5	ie
DISSOLVED OXVQEN - MG/l
15

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Figure 19. Average vertical dissolved oxygen saturation level profile at
Ford Rock (Spokane River Mile 103.3) during Surveys I, II, III,
i\i	'


)
SURUEV I
SURVEY II
SURUEV III
SURUEV IU
/
20	40	60	80	100
DISSOLVED OXYGEN - * SATURATION

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Conductivity and pH
Conductivity and pH were measured during Surveys II, III, and IV, only.
Conductivity showed little variation during the period from July 31,
1979, to September 20, 1979. Maximum conductivity was 70 umho/cm and
minimum conductivity was 50 umho/cm.
pH levels varied from a low of 6.3, in the deep water at Ford Rock, to a
high of 7.6 in the surface water near the outlet of Lake Coeur d'Alene.
In general, the high pH levels corresponded to high dissolved oxygen, and
low pH to low dissolved oxygen.
Nutrients
Concentration of the various forms of nitrogen and phosphorus were
measured during Surveys II (July 31, 1979) and IV (September 18-20,
1979). Inorganic nitrogen levels (NH^-N and NO^+NO^-N) were less
than 0.03 mg/1 during both surveys. During Survey II 70% of the samples
had concentrations of NO^+NO^-N less than the detection limit of 0.01
mg/1. 483. of the samples were below the detection limit for
NO2+NO3-N during Survey IV.
Dissolved orthophosphate was equal to, or less than, 0.02 mg/1 at all
sample stations during Surveys II and IV. During both surveys, however,
the sampling stations upstream from the Coeur d'Alene sewage treatment
plant had concentrations which were less than the level of detection,

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0.01 mg/1, while at the station just downstream from the plant we found
concentrations of 0.02 mg/1 in all samples collected.
Total phosphorus (Figures 19 and 20) and, to a lesser degree, total
nitrogen (Figures 21 and 22) were influenced by the discharge from the
City of Coeur d'Alene's treatment plant. In Survey II, average total
phosphorus in the Spokane River increased from 0.024 mg/1 to 0.038 mg/1
at stations upstream and downstream, respectively, from the treatment
plant. The corresponding increase during Survey IV was from 0.011 mg/1
to 0.056 mg/1.
For total nitrogen the increase was from 0.33 mg/1 to 0.38 mg/1 during
Survey II and from 0.16 mg/1 to 0.36 mg/1 during Survey IV.
Total Organic Carbon
The results of in-stream measurements of total organic carbon are shown
in Figures 23 and 24 for Surveys II (July 3!-August 2, 1979) and IV
(September 18-20, 1979). Values ranged from 1 mg/1 to 8 mg/1, with the
highest values occurring at the Harbor Island sampling station (R.M.
106.5). During Survey IV, total organic carbon concentrations were very
nearly uniform from the outlet of Lake Coeur d'Alene to Post Falls Oam,
varying from 1 mg/1 to 2 mg/1.
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Figure 20. Average, maximum and minimum total phosphorus concentrations in
the Spokane River during Survey II (July 31 - August 2, 1979).
0.14
0.12
T 0.10
0
T
A
L 0.08
I
U>
0.06
11
6
L .e4
0.02
103 104 105 106 10? 108 109 110 111 112
SPOKANE RIUER MILE

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Figure 21. Average, maximum and minimum total phosphorus concentrations in
the Spokane River during Survey IV (September 18-20, 1979).
I
U>
I
T
0
T
A
L
II
G
/
L
0.14
0.12 -
0.10 -
0.08 -
0.06
0.04 -
0.02
103 104 105 106 107 108
109
110 111
112
SPOKANE RIUER MILE

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Figure 22. Average, maximum and minimum total nitrogen concentrations in
the Spokane River during Survey II (July 31 - August 2, 1979).
1.2
1.0
I
U>
cn
i
T
0
T
A
L
N
0.8
0.6
II
G 0.4
/
0.2
-

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k




<
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i
103 104 105 106 107 108 109 110 111 112
SPOKANE RIUER MILE

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Figure 23. Average, maximum and minimum total nitrogen concentrations in
the Spokane River during Survey IV (September 18-20, 1979).
1.2
1.0
T
0 0.8
T
a
L
N 0.6
II
G 0.4
/
L
0.2
103 104 105 106 107 108 109 110 111 112
SPOKANE RIUER MILE
1 1 1 1
i i
iii-
-

t
i
I
1 I
*
*
*
* , '
i i i i
 i
i i i

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Figure 24. Average, maximum and minimum total organic carbon concentrations
in the Spokane River during Survey II (July 31 - August 2, 1979).
IS.6
I
U>
I
T
0
T
A
L
0
R
G
A
N
1
C
C
A
R
B
0
N
11
G
/
L
10.5 -
8.4 -
6.3 -
4.2 -
2.1
163 104 105 106 107 108 109 110 111
112
SPOKANE RIUER MILE

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Figure 25. Average, maximum and minimum total organic carbon concentrations
in the Spokane River during Zurvey IV (September 18-20, 1979).
i i i i i	1	r
-* * * 
J	I	I	I	I	I	I	I	L
!
f i
103 104 105 106 107 108 109 110 111 1 IS
SPOKANE RIVER MILE

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Carbonaceous Biological Oxygen Demand fBOD^
Ultimate BOD and rates of deoxygenation were determined from standard,
uninhibited 5-, 10-, 15-, and 20-day BOO measurements made during Surveys
II (July 31-August 2, 1979) and IV (September 18-20, 1979K The results,
obtained using the method of Moore et al H950), are shown in Figures 25
and 26, and Tables 5 and 6.
Table 5 Ultimate 800 and deoxygenation rates in the Spokane River
estimated from s^amples collected during Survey II
(7/31/79-8/2/79). The method of moments (Moore et al H950))
was used to estimate these parameters from average values of 5-,
10-, 15-, and 20-day BOO measurements
Spokane	Ultimate BOO	Deoxygenation Rate
River Mile
(mg/1)
(days-1, base
111.0
1.62
0.28
109.7
1.57
0.24
108.6
2.73
0.25
106.5
1.49
0.19
105.4
1.64
0.1"?
104.4
1.60
0.12
103.1
2.77
0.06
102.5
1.80
0.14
102.2
1.89
0.0
Table 6 Ultimate BOD and deoxygenation rates in the Spokane River
estimated from samples collected during Survey IV
(9/18/79-9/20/79). The method of moments fMoore et al M950I)
was used to estimate these parameters from average values of
10-, 15-, and 20-day 800 measurements
Spokane	Ultimate BOD	Deoxygenation Rate
(days' , base e)
0.15
0.09
0.12
0.1 3
0.07
0.08
0.'3
River Mile
(mg/1)
110.0
1.56
109.7
1.98
108.6
2.11
106.5
1.88
104.4
1.93
103.1
2.02
102.2
] .37
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Figure 26. Average, maximum and mjnimim ultimate BOD concentrations in the
Spokane River during Survey II (July 31 - August 2, 1979).
IS
I
0
1
u
L
T
I
n
A
T
E
B
0
D
11
G
/
L
10 -
8
6 -
103 104
105 106 107 108
SPOKANE RIUER MILE
109
110 111
112

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Figure 27. Average, maximum and mini nun ultimate BOD concentrations 1n the
Spokane River during Survey IV (September 18-20, 1979).
105 106 10? 108
SPOKANE RIVER fllLE
112

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Point Sources
Spokane River
Measurements of total organic carbon, total nitrogen and phosphorus,
ultimate BOD at the outlet of Lake Coeur d'Alene (R.M. 111.0) reflect the
background water quality characteristics of the Spokane River. Mass
loadings of these constituents, as measured at River Mile 111.0 during
Surveys II and IV, are shown in Table 7.
Table 7 Estimated loading rates of total organic carbon, total
phosphorus, total nitrogen and ultimate BOD from Lake Coeur
d'Alene during Survey II (7/31/79-8/2/79) and Survey IV
(9/18/79-9/20/79)
Loading Rate
(lbs/day)
Constituent	Survey II	Survey IV
Total organic carbon	17700	16200
Total phosphorus	44	81
Total nitrogen	930	1290
Ultimate 80D	7190	12600
The river flows, Qqq|_, used to compute these loadings were estimated
from:
QCDL = QPF + QRP + QGW
Where,
Qpp = the discharge of the Spokane River below Post Falls (Table
4), c.f.s.
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Table 8 Concentrations and estimated loadings* of total organic carbon, total KJeldahl nitrogen, ammonia-nitrogen, nitrite-plus
nitrate-nitrogen, dissolved orthophosphate and total phosphorus for the Coeur d'Alene sewage treatment plant durinq Survey II
(7/31/79-8/2/79) and Survey IV (9/18/79-9/20/79)
Date
T ime
Dally Average
Type of Flow	TOC	TKN	NH3-N	N02-+N03-N
Sample (mgd) (mg/l)(lbs/day) (mg/1)(lbs/day) (mg/1)(lbs/day) (mg/1)(lbs/day)
POa-P
(mg/1Hlbs/day)
Total P
fcng/llMbs/dav^
Survey II
7/30//9~l715-
7/31/79 0930 Composite 2.06
7/31/79 0930-
8/1/79 0955 Composite 2.12
8/3/79 0930 Grab	2.13
29
30
514
534
10.2
17.6
6.5
112
6.0
103
7.6
131
7.8
134
8.6
152
6.0
106
7.4
131
7.2
128
7.8
138
10.4
185
6.4
114
8.6
153
7.1
126


Survey IV
9/18/79 1000
Grab
1.91
28
447
5.9
94






7.3
116
9/19/79 1000
Grab
1.93
24
387
6.0
97
2.6
42
13.2
213
7.0
113
7.7
1?4
9/20/79 0930
Grab
1.80
24
361
12.3
185
2.7
41
12.8
192
7.5
U3
8.0
IPO
OJ
I
* Estimated loadings are based upon dally average flow from the sewage treatment plant

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Q^p = the water diverted for irrigation use in the Rathdrum
Prairie Project (Table 4), c.f.s.
Qgw = 150 c.f.s., the amount of water which the USGS estimates
is lost to the groundwater between Coeur d'Alene and Post
Falls.
City of Coeur d'Alene STP
Single grab samples, as well as 24 hour composite samples, of treated
effluent were collected from the City of Coeur d'Alene's sewage treatment
plant during Surveys II and IV. Concentrations and estimated loadings of
total organic carbon, total Kjeldahl nitrogen, ammonia-nitrogen, nitrite-
plus nitrate-nitrogen, dissolved orthophosphate and total phosphorus are
given in Table 8. 5-, 10-, 15-, and 20-day BOO measurements were also
obtained from these samples. However, the results of the measurements
suggested that the waste contained constituents which made the BOD test
unreliable. For example, as shown in Table 9, the 5-day 800 increased as
the waste was diluted. Attempts at estimating deoxygenation rates for
the treatment plant effluent were thwarted by the odd behavior of the BOO
assays, as shown in Table 10.
Table 9 5-day BOD as a function of dilution for samples collected from
the City of Coeur d'Alene sewage treatment plant on 7/31/79 and
8/1/79.
5-day BOD
Dilution Level	(mg/1)
%	7/31/79 Sample	8/1/79 Sample
0.5	98	268
2.5	45	47
5.0	31	27
10.0	24	18
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Table 10 5-, 10-, 15-, and 20-day BOO measurements of samples collected
from the City of Coeur d'Alene sewage treatment plant on
7/31/79 and 8/1/79.
Dilution 3-day BOD 10-day BOD 15-day BOD 20-day 800
Sample Date
(*)
(mg/1)
(mg/1)
(mg/1)
(mg/1)
7/31/79
2.5
45
29
74
64
8/1/79
0.5
268
130
224
58
Trophic Status
Water Clarity
Water clarity, as measured by the depth at which a Secchi disk
disappears, is shown in Figure 28. Data include only those stations for
which water depth was greater than the Secchi disk reading.
The minimum Secchi disk reading during the four surveys was 10 feet and
the maximum, 20 feet. Dillon and Rigler (1975), who compared Secchi disk
readings with chlorophyll a concentrations for a number of lakes in
southern Ontario, found for readings of 10 feet and greater, chlorophyll
a concentrations were less than 5 ug/1. Lorenzen (1979\ analyzing data
collected during EPA's National Eutrophication Survey (NES^ from lakes
throughout the United States, found chlorophyll ^ concentrations were
less than 10 ug/1 for all lakes with readings greater than 10 feet.
Given these findings, and trophic classifications based upon chlorophyll
a (Chapra and Tarapchak (1976)1, the Spokane River between Post Falls
would be classified oligotrophic to merotrophic.
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Figure 28. Water clarity in the Spokane River during Surveys r, TT
III and IV as measured by Secchi disk depths.


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DEC JAN FEB MAR APR HAY JUN JUL AUQ SEP OCT NOV

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Aquatic Plants
During Survey IV we made a survey of the approximate area! extent of the
aquatic plant conmunity. We performed this survey from the boat while
moving slowly along the river bank. We took no samples, and our
assessment was based only upon our judgment of the relative abundance and
areal extent of the plants. According to Professor Michael Falter
(personal communications) of the University of Idaho, the predominant
plant is a species of Equisetum (horsetail). Figure 29 shows the results
of the survey.
Algal Assay
In an effort to determine the potential for algal growth in the Spokane
River above Post Falls, we collected water samples for the static algal
assay, as developed by Miller, Greene and Shiroyama C1978K We collected
these samples during Survey IV at two locations, one at the outlet of
Lake Coeur d'Alene, the other just upstream from Post Falls Oam. The
sample at each of the two stations was a composite of water taken from
the surface, mid-depth and bottom.
A major conclusion from the assay, according to Cummins et al nQ80^, was:
"The samples of Spokane River water assayed could be considered to be
only moderately productive based on a productivity classification
linked to the 14-day standing crop of S^ capricornutum by
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Post Falls
Spokane River

I
00
1
Scale in. Mijes
J4
Relative Concentration of
Equlsetum (Horsetail)
Figure 29
Qualitative Assessment of
Equisetum in the Spokane
River During the Water
Quality Survey of
September 18-20,1979.
D'Alene
Lake Coeur D'Alene

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Miller, Maloney and Greene (1974). Although the addition of nitrogen
alone resulted in increased algal growth during the assay, the
evaluation of the effect of increased nitrogen or phosphorus
concentrations on the productivity of the River itself 1s complicated
by the possible presence of substances Inhibiting algal growth."
Effects of Land and Water Use
The Spokane River between Coeur d'Alene and Post Falls is used for
transportation, recreation, fishing and the generation of hydroelectric
power. All of these water uses, as well as their associated riparian
land use, have some impact upon the quality of the Spokane River. During
our four surveys, however, it appeared the major impact, both upon the
Spokane River and the land adjacent to it, was from the transportation,
handling and processing of logs.
At times during all four of our surveys there were large amounts of
sawdust, bark and logs floating in the river. In the vicinity of the
sawmills and log handling areas, the river bank was highly disturbed. We
made no attempt to measure the impacts of careless log handling
practices. It Is clear, though, that with respect to aesthetics and
normal boat traffic the impact is substantial. The impact of the organic
matter and nutrient upon water may be important,- as well, and should be
given consideration equal to that of the discharge of domestic wastes.
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CONCLUSIONS
1.	The morphology of the Spokane River's bottom, with fairly deep
isolated holes at Ford Rock and behind Post Falls Dam, has
substantial impact upon water quality during low flow.
2.	Dissolved oxygen levels were between 81% and 90% saturation during
Survey I, varied from 33% to 113% during Survey II, from 2% to 108%
during Survey III, and from 86% to 101% during Survey IV. The
veritlcal and longitudinal distribution of dissolved oxygen was
fairly uniform during Surveys I and IV. During Surveys II and III
when river flow was low and water temperature high, the dissolved
oxygen decreased with depth, particularly below 10 meters, and with
distance downstream. Vertical depression of dissolved oxygen was as
much as 7.4 mg/1 and average longitudinal depression as much as 2.0
mg/1.
3.	Water temperature greater than 20C were common during Surveys II,
III, and IV. During Survey I they varied from 4.0C to 5.1C.
Temperatures were generally uniform throughout Surveys I and IV,
although there was some surface heating which elevated temperatures
during Survey IV. During Surveys II and III water temperature
decreased with depth as much as 5.1C at Ford Rock. Surface
temperature increased downstream from the outlet of Lake Coeur
d'Alene as much as 1.5C during Survey II.
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Levels of nitrogen and phosphorus were generally low throughout the
Spokane River from the outlet of Lake Coeur d'Alene to Post Falls
Dam. Total phosphorus, though at low levels, was substantially
higher downstream from the City of Coeur d'Alene's sewage treatment
plant than it was upstream.
Algal assays of samples collected during Survey IV showed the Spokane
River to be moderately productive. The evaluation of the assay,
however, was complicated by the presence of substances inhibiting
algal growth.
Water and riparian land uses associated with the transportation,
handling and processing of logs have substantial impact on other
water uses. The effect on aesthetics and normal boat traffic is
particularly severe. The effect upon water quality is not known but
warrants further investigation.
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BIBLIOGRAPHY
Chapra, S.C., and S.O. Tarapchak, A chlorophyll a model and its
relationship to phosphorus loading plots for lakes, Water Resources
Research, 12(6), 1260-1264, December 1976.
Cummins, J.M., C.E. Gangmark, and M.R. Krier, Results of freshwater algal
assays conducted on water samples collected from the Spokane River,
Idaho, September 20, 1979, U.S. Environmental Protection Agency,
Surveillance and Analysis Division, Manchester, Washington, 14 pp.,
March 28, 1980.
Dillon, P.J., and F.H. Rigler, A simple method for predicting the
capacity of a lake for development based on lake trophic status, J.
Fish. Res. Bd. Can., Vol. 32(9), 1519-1531, 1975.
Drost, B.W., and H.R. Seitz, Spokane Valley-Rathdrum Prairie Aquifer,
Washington and Idaho, U.S. Geological Survey Open-File Report 77-289,
1978.
Lorenzen, M.W., Effect on phosphorus control options on lake water quality
EPA Office of Toxic Substances, EPA-560/11-79-011, September 1979.
Miller, W.E., J.C. Greene, and T. Shiroyama, The Selenastrum
capricornutum Printz bottle test (Experimental design, application
and data interpretation protocol). Corvallis Environmental Research
Laboratory, Corvallis, Oregon, EPA-600/9-78-018, 126 pp., 1978.
Miller, W.E., T.E. Maloney, and J.C. Greene, Algal productivity in 49 lake
waters as determined by algal assays, Water Research, Vol. 8,
667-679, 1974.
EPA, Methods for chemical analysis of water and wastes, Environmental
Monitoring and Support Laboratory, Cincinnati, Ohio,
EPA-600/4-79-020, March 1979.
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